Almost from the advent of the first motor vehicle powered by an internal combustion engine, engine speed control has been effected by an accelerator pedal mechanically coupled through the vehicle fire wall to an engine "speed regulator" such as a carburetor. When no pressure is applied to the pedal, the engine runs at some preset idle speed. And when vehicle-accelerating pressure is applied to the pedal, the pedal/carburetor linkage opened passages in the carburetor to admit more fuel to the engine. The linkage is "custom-configured" for the particular vehicle, engine and carburetor.
Much more recently, engine and vehicle manufacturers have turned to electrical and electronic engine speed control systems which sense engine temperature, engine load and the like and automatically control pump-fed fuel injectors to cause the proper amount of fuel to be admitted to the engine. Such systems are vastly more flexible in the way they can be installed in the vehicle and applied in the engine ignition system.
As but one example of improved flexibility in application, it is no longer required to extend a mechanical linkage through the vehicle firewall and provide appropriate sealing devices to prevent air leakage into the passenger compartment. Rather, electrical wires can be extended from the accelerator pedal mechanism to the electronic speed control on the engine.
A typical electrical engine throttle control system uses an electrical sensor, the output signal of which is a function of the position of the accelerator pedal. That is, the sensor "senses" pedal position between idle speed and maximum engine speed and the resulting signal is used by the electronic engine speed control system for engine speed regulation. A common sensor is embodied as a potentiometer or "pot" having a rotating stem. As the accelerator pedal is depressed and released, the stem rotates and an appropriate output signal results.
Examples of electronic accelerator pedal mechanisms having a foot pedal and a sensor coupled thereto are disclosed in U.S. Pat. No. 4,958,607 (Lundberg); U.S. Pat. No. 4,976,166 (Davis et al.); U.S. Pat. No. 5,133,225 (Lundberg et al.); U.S. Pat. No. 5,237,891 (Neubauer et al.); U.S. Pat. No. 5,241,936 (Byler et al.) and U.S. Pat. No. 5,321,980 (Hering et al.). U.S. Patent No. 5,133,321 (Hering et al.) discloses a resistive-type throttle control and idle-validation sensor combined into a single component.
While earlier mechanisms have been generally satisfactory for the intended use, they are not without disadvantages. For example, mechanisms of the type shown in the Davis et al. and Neubauer et al. patents have a base fixed with respect to the vehicle. As the accelerator pedal moves, a roller rolls along the base. Dirt or gravel, commonly found in the cabs of construction and mining vehicles, can lodge between the roller and the base. The result is that the position of the roller may "jump" with respect to the base (that is, the roller may temporarily be out of contact with the base) and a false potentiometer signal results.
Other disadvantages arise, in part, because of the configuration and manner of use of the equipment on which the mechanism is mounted, i.e., the ergonomics of the application. (Ergonomics is the science that seeks to adapt work or working conditions to suit the worker.)
For example, many types of equipment, e.g., off-road construction and mining equipment, are, for a particular piece of equipment, used by several different operators. Of course, this may give rise to differing ergonomic considerations in that such operators may have widely-varying preferences as to accelerator pedal position and may have widely-varying physical statures.
Earlier accelerator pedal mechanisms of the electronic type employ a base fixed with respect to the vehicle. The angle of the accelerator pedal in its "engine-idle" position is fixed with respect to the base and with respect to any seat upon which the operator may be seated. A pedal angle which is ideal for one operator of a particular stature may be uncomfortable, especially over a long operating period, for another operator having a significantly different stature.
And there are other important considerations. Road grader operators like to operate the grader while standing. This means that in both the engine-idle and maximum-speed positions, the accelerator pedal is preferably at no more than a shallow angle with respect to the floor upon which the operator stands.
In sharp contrast, some low-profile mining machines are configured so that the operator is in a near-reclining position behind the accelerator pedal. For that type of machine, the accelerator pedal is preferably nearly vertical in both the engine-idle and maximum-speed positions. Known accelerator pedal mechanisms are not readily responsive to these needs.
Yet another disadvantage of some electronic accelerator pedal mechanisms is that the pedal assembly hardware must be configured to accommodate a particular sensor made by a particular manufacturer. For example, the combined control and validation sensor disclosed in the above-noted Hering et al. patent is to be used with Cummins CELECT.TM. electronic fuel control system. The patent goes on to explain that the sensor may be "adapted" to operate with a variety of control systems and control devices. But, of course, this does not necessarily mean that the pedal assembly hardware can easily be adapted to use any one of a variety of sensors.
Still another disadvantage of some electronic accelerator pedal mechanisms is that pedal operation flexes the electrical cable extending between the sensor and the electronic ignition system. The foot pedal disclosed in the above-noted Davis et al. patent is of this type.
An improved vehicle accelerator pedal apparatus which addresses disadvantages of prior art arrangements would be an important technical advance.